There was discussion on pgsql-general a bit before the release. It appears that physically sequential scan of a table is about as fast as key-order sequential

There was discussion on pgsql-general a bit before the release. It appears that physically sequential scan of a table is about as fast as key-order sequential scan of a covering index. To speed up a lot, I think you'd need to be able to scan an index in physical order which is not currently supported. Now if you are using SSD's yeah, you could tweak the planner settings enough to cause it to make an index scan perhaps, and maybe you'd see a modest performance increase, but even there it appears the operating system's prefetch logic really does come to the rescue of a sequential scan of a table in physical order.